Stem cells are undifferentiated, or immature cells that are capable of giving rise to multiple, specialized cell types and ultimately to terminally differentiated cells. Unlike any other cells, they are able to renew themselves such that essentially an endless supply of mature cell types can be generated when needed. Due to this capacity for self-renewal, stem cells are therapeutically useful for the regeneration and repair of tissues and organs. Stem cells have the potential for providing benefit in a variety of clinical settings.
Stem cells are classified according to their differentiation potential as pluripotent and multipotent. Embryonic stem cells (ESC) are well-known as a pluripotent stem cell, which can be differentiated into almost any type of cells in the organism. Multipotent stem cells such as bone marrow stem cells exist in the adult body. Although their growth and differentiation potential is limited, they are considered to play important roles in self-repair of damaged tissues. Translating these advantages of stem cells into clinical benefits faces many challenges, including efficient proliferation and differentiation into the desired cell type(s), maintaining genetic stability during long-term culture and ensuring the absence of potentially tumorigenic ESC from the final product. Modulation of growth and differentiation with low molecular weight compounds is one of the solutions for these problems.
Prostaglandins (hereinafter, referred to as PG(s)) are members of class of organic carboxylic acids, which are contained in tissues or organs of human or other mammals, and exhibit a wide range of physiological activity PGs found in nature (primary PGs) generally have a prostanoic acid skeleton as shown in the formula (A):

On the other hand, some of synthetic analogues of primary PGs have modified skeletons. The primary PGs are classified into PGAs, PGBs, PGCs, PGDs, PGRs, PGFs, PGGs, PGHs, PGIs and PGJs according to the structure of the five-membered ring moiety, and further classified into the following three types by the number and position of the unsaturated bond at the carbon chain moiety:
Subscript 1: 13,14-unsaturated-15-OH
Subscript 2: 5,6- and 13,14-diunsaturated-15-OH
Subscript 3: 5,6-, 13,14-, and 17,18-triunsaturated-15-OH.
Further, the PGFs are classified, according to the configuration of the hydroxyl group at the 9-position, into α type (the hydroxyl group is of an α-configuration) and β type (the hydroxyl group is of a β-configuration).
PGs are known to have various pharmacological and physiological activities, for example, vasodilatation, inducing of inflammation, platelet aggregation, stimulating uterine muscle, stimulating intestinal muscle, anti-ulcer effect and the like.
Some 15-keto (i.e., having oxo at the 15-position instead of hydroxy)-PGs and 13,14-dihydro (i.e., having single bond between the 13 and 14-position)-15-keto-PGs are known as the substances naturally produced by the action of enzymes during the metabolism of primary PGs.
However it is not known how the prostaglandin compound acts on the stem cells.